Thermionic amplifying circuits



June 7, 1932. E. ASCH THERMIONIC AMPLIFYING cmcun's Filed 001:. 24, 1928,

Patented June 7, 1932 UNITED- STATES mucn PATENT OFFICE ASOH, OI lBERLlN-sUDENDE, GERMANY, ASSIGNOR '10 RADIO PATENTS CORPO- RATION, OF NEW YORK, 11'. Y., A CORPORATION OF NEW YORK THERMIONIC AMPLIFYING CIRCUITS Application filed October 24, 1828, Serial No.

This invention relatesto the amplification of weak electric voltages by means of thermionic tubes and it consists in an arrangement which is very simple, which allows a high amplification to be obtained and which requires one single source of current. The invention comprises the method of connections and the proper dimensioning of the various electrical parts hereinafter referred One object of the invention is to amplify -weak direct current or alternating voltages,

another object being'the conversion of weak alternating current voltages nto cont nuous currents, whilst a further ob]ect Is the provision of receiving means for wireless apparatus.

Figures 1-6 of the accompanying drawing illustrate, diagrammatically and by way of example, various arrangements according to the present invention, whilst Figure 7 shows a detail.

A fundamental arrangement according to the invention is illustrated in Figure 1, in

which m and n are the poles of a source of current, more particularly continuous cur rent; a is an amplifying thermion c tube, more particularly a tube having a high amplification factor; b is a second amplifying thermionic tube; 1' i" a very high ohmlc resistance; 11, 12, 13 and 14 are ohmic resistances and 2 is an apparatus on which the I amplification current acts and which may be a loudspeaker, a telephone, a relay, an electromagnet, or the primary winding of a transformer.

As will be seen from the drawing, the anode of the thermionic tube a is connected directly to the grid of the thermionic tube 6 v and over the resistance r to the positive pole n of the source of current. The apparatus 2 lies in the connection between the anode of the tube band the positive pole n of the source of current." The filaments of the two being necessary only when the tube a re- .814368, and in Germany November 10, 1927."

quires a current for its filament which is weaker than the. sum of the heating current and of the emission current of the tube 6.

The resistances 11, 12 and 13 serve for the purpose of adjusting the grid voltage \of the tubes (2 or b to the required value. The potential of the anode of the tube a must lie between the potential of the two filaments) The resistance 14 takes up the largest portion of the voltage of the source of current. The resistance, 11 may be dispensed with, in which casethe resistance 12 serves for adjusting the internal resistance of the tube a to the desired value. The voltage to be amplified is supplied to the points 11:, and 3 between the pole at and the grid of the tube a. A

' thermo-element e is inserted between these points by way of example.

It is essential that the resistance 1' shall be about 10 times, in practice 5 to 20 times, greater than the internal resistance of the tube a. In this way it is attained that only one-tenth of the voltage of the source of current m, n is applied to the tube a, so that practically the whole of the voltage is applied to the tube 6. If the voltage between the poles m and nis, for instance, 220 volts, the voltage applied to the tube a will be about 15-30 volts and the resistance 1' will have a value of about 10-50 megohms.

Let us assume that the thermo-element is heated and that it produces a voltage which causes the grid of the tube a to become more positive. In that case, the internal resistance of the tube a will drop, itsanode and the grid of the tube 1) will become more negative than they were before, the internal resistance of the tube 1) will be increased and the current in theapparatus zdecreased. The opposite effect will be produced if the'thermo-element produces a voltage in the opposite direction. By using a desired receiving thermionic tube, the amplification can easily be made so high that when the voltage on the grid of the tube It varies, the anode current of the tube 6 varies by about 10 milliamps or more.

According to the arrangement illustrated in Figure 2, the thermo-element e or any other direct current voltage desired to be amplified is inserted in the connection between the pole m of the source of current and the filament of the tube a, the grid of thesaid tube being connected directly tovthe pole m.

The amplification arrangement is also very sensitive to any variation in the resistance 11, which may also be used in certain cases.

The voltage consumed by the tube a reduces thevoltage applied from the source of current to the tube 6. In order further to reduce the voltage applied to the tube a, according to Figure 3, the tube a is provided in a known manner with a space charge grid g, which is connected to a morepositive point of the heating circuit, for instance to the filament of the tube 6.

If an alternating current voltage is applied to the points m and y instead of a direct current voltage, for instance means of a transformer, as shown in Figure 4, the said alternating current voltage is also amplified like the continuous current voltage. In that case, the apparatus a may be an alternating current relay, a loudspea er, or the like. In contradistinction to the most known diagrams of connections, in the present arrangement the amplification is independent of the frequency of the alternating current within the widest limits in consequence of the direct connection of the anode of the tube a to the grid of the tube 6. In the case of alternating ,current and more particularly of a high frequency current, a second effect is produced, viz., the rectification in the tube a in such a manner that the anode current is reduced in the tube 6 so long as an alternating current voltage is applied" to the points so and y.

us, if z is a direct current measuring instrument, the deflection of the same will go back accprding to the alternating current voltage supplied to thegrid of the tube a.

The ratio between this alternating current,

voltage and the variation in the anode current of the tube 6 is about the same as in the arrangements hereinbefore described and may be referred to as the amplification factor.

The capability of the arrangements above described of rectifying the alternating current renders the amplifier suitable-also for the reception of wireless telegraphy and telephony. For the reception of wireless telegraphy y means of a Morse apparatus or for wireless distant control, the apparatus 2 would consist of arelay, and if it is desired to measure the strength of the incoming signals or of disturbances, use is made of a continuous current galvanometer. In the case of wireless telephony or reception of wireless telegraphy by sound, the apparatus ,2 may consist, for instance, of a loudspeaker, or of a low frequency amplifier operating a loudspeaker. In the case of wireless telephony, a loudspeaker and a galvanometer may be connected in series with one another in the output circuit of the tube 6, so as to be able to ascertain from the deflections of the galva- I come into question in wireless telegraphy or telephony, and Figure 5 shows a high frequency oscillatory circuit comprising a selfinductance s and variable capacity 0 inserted between the pole m of the source of current and the grid of the tube a.

In the case of reception of high frequency currents, the' anode circuit of the tube 6 is energized not only by direct current, which in wlrelesstelephony goes up and down according to the sounds received, but also am- Elified high frequency currents. t is possile to arrange that the latter shall react on the grid of the tube a in a known manner in order to increase the sensitiveness of the receiver. Such an arrangement is illustrated in Figure 6. The coil ;0 inserted in the aerial circuit h as Well as the coil 9 which is connected in series with the apparatus 2 in the anode circuit of the tube 6 actinductively upon the coil 8 which is connected in parallel with a variable condenser 0 between the pole m of the source of current and the grid of the tube a. As usual, the apparatus 2 is shunted by a condenser k to facilitate the passage of high frequency currents.

In order that the high frequency current should flow through the anode circuit of the tube 12 it is necessary that the resistance r shall not be bridged over by a condenser. Even a very small capacity would be sufficient to practically short-circuit it. Therefore if it is desired to-use reaction, the "connection between the anode of the tube a and the grid of i the tube I) should be made asshort as possible. A suitable way to obtain this object consists in combining thetwo tubes in a single tube in such a manner that the plate or anode of the first set of electrodes corresponding to the first tube acts as a grid or control electrode for the second set of electrodes corresponding to the second tube. This arrangement is illustrated diagrammatically in F igure 7, in which 9 illustrates an evacuated glass vessel containing filaments 16 and 19, corresponding to the filaments of tube a and tube 6 respectively, according to Figure 1, a grid'electrode 17' and anode 18 cooperating with the filament 16. 20 is the second anode corresponding to the anode of the tube 6, according to Figure 1. The filament 19 is arranged intermediate the anodes 18 and 20, so that the anode 18 acts as a control member for the discharge current from the filament 19 to the anode 20 in a manner similar to single discharge tubes of this type in which the grid or control electrode is arranged at the opposite side of the cathode,'or outside the path of the discharge current from the cathode to the anode. This type of multiple tube may one of the preceding circuits, as is obvious, whereby the anode 18 is e uivalent to the common connecting point 0% the anode of tube a and the grid of tube 1), according to the previous circuits In order to obtain a high amplification factor in the construction illustrated in Figure 7 the con trolling electrode and the filament must be laced as close as possible to one-another and 1t is therefore an advantage to secure the latter to the controlling electrode by means of an insulating substance which is not affected by heat.

In all the arrangements hereinbefore described, it has been assumed that thesource of current m, n is a source of continuous current. However, when it is only a question of measuring or of signals and not of the reception of wireless telephony, it is possible to operate the amplifier by means of alternating current. In that case only the one half.- period of the since the tube itself operates as a known manner.

The arrangements hereinbefore described be connectedin any a rectifier in may be modified in various respects without,

in any way departing sco e of the invention.

l1 hat I claim is 1-- 1. An arrangement for the amplification of weak direct current voltages and for the amplification and rectification of weak alternating current voltages, comprising a source of direct current, two thermionic tubes, a high resistance which connects the anode of the first thermionic tube with the positive pole of the source of current, resistances which are connected to the source of current in series with the filaments of the two ther-' mionic tubes and a sensitive apparatus in the output circuit of the second thermionic tube, the anode of the first thermionic tube being connected directly to the grid of the second tube, the said high resistance being about 10 times larger than the efiective resistance of the first thermionic tube and the part of the circuit receiving the voltages to be amplified being connected to the grid of the first thermionic tube. i v

2. An arrangement for the amplification of weak direct current voltages and for the amplification and rectification of weak alternating current voltages, comprising a source of direct-current, two thermionic tubes of which the first one has a space charge grid, a high resistance which connects the anode of the first thermionic tube with the positive pole of the source of current, resistances which are connected to the source of current in series with the filaments of'the two thermionic tubes, and a sensitive apparatus in the output circuit of the second thermionic tube,

fromthe spirit and the anode of the first thermionic tube being connected directly tothe grid of the second tube, and the space charge. grid of the first alternating current is operative tube being connected to a pointof the circuit 3. An arrangement for the amplification or measurement of weak direct current voltages or variations of direct current voltages,

comprising a source of direct current, two thermionic tubes, a high resistance which connects the anode of the first thermionic tube with the positive pole of the source of current, resistances which are connected to the source of current in series with the fila ments of the two thermionic tubes anda sensitive apparatus in the output circuit of the second thermionic tube, the anode of the first thermionic tube being connected directly to thegrid of the second tube, the said high resistance being about 10 times larger than the effective resistance of the first thermionic tube, the part of the circuit receiving the voltages to'be amplified being connected to the grid of the first thermionic tube and the said sensitive apparatus consisting of a measuring instrument, relay or electromagnet for continuous current.

4. in an electrical system, a first thermionic tube having anode, cathode, and control electrodes; a second thermionic tube having anode,- cathode, and control electrodes; a source of energy; a direct conductive connection from the anode of said first tube to the control electrode of said second tube; means including circuit connections for connecting the anode circuits of said tubes in parallel across said source of energy,

5. In an electrical system, a first thervmionic tube having anode, cathode, and control electrodes; a second thermionic tube having anode, cathode, and control elec-' trodes; a source of energy;- a direct conductive connection from the anode of said first tube to the control electrode. of said second tube; means including circuit connections for connecting the anode circuits of said tubes in parallel across said source of energy; and resistance means connected in said circuit connections for maintaining predetermined potential relations of said electrodes. 6. In an electrical system,'a first thermionic tube having anode, cathode, and control electrodes; a second thermionic tube haV- ing anode, cathode, and control electrodes; a source of energy; means for directly conductively connecting the anode electrode of said first tube to the control electrode of said second tube; means including circuit connections from the anode electrode of each of said tubes to one terminal of said source of energy; means including circuit connections from the cathode electrodes of of each of said tubes to one terminal of said source of energy; and a resistance means connected in the anode electrode circuit connections.

7. In an electrical system, a first thermionic tube having anode, cathode, and control electrodes; a second thermionic tube, having anode, cathode, and control electrodes; a source of energy; means for directly conductively connecting the anode electrode of said first tube to the control electrode of said second tube; means including circuit connections from the anode electrode of each of said tubes to one terminal of said source of energy; means including circuit connections from the cathode electrodes of said tubes to the opposite terminal of said source of enegy; and a resistance means connected in the anode electrode circuit connections; and a resistance means connected in the cathode electrode circuit connections.

8. In an electrical system, a first thermionic tube having anode, cathode, and control electrodes; a second thermionic tube having anode, cathode, and control electrodes; a direct conductive connection from the anode of said first tube to the control electrode of the second tube; a source of energy for supplying potentials to said electrodes; means ,including circuit connections from said anodes to the positive terminal of said source of en rgy; and resistance means in said circuit connections for maintaining the anode potential of said first tube in predetermined relation with respect to the anode potential of the second tube.

9. In an electrical system, a first thermionic tube having anode, cathode, and control electrodes; a second thermionic tube having anode, cathode, and control electrodes; a direct conductive connection from the anode of said first tube to the control electrode of the second tube; a source of energy for supplying potentials to said electrodes; means including circuit connections from said anodes to the positive terminal of said source of energy; resistance means in said circuit connections for maintaining the anode potential of said first tube in predetermined relation with respect to the anode potential of the second tube; means including circuit connections from thecathodes of said tubes to the negative terminal of said source of energy; and resistance means in said last mentioned circuit connection for maintaining predetermined relations between said cathodes.

10. In an electrical system, a first thermionic tube having anode, cathode, and control electrodes; a second thermionic tube having anode, cathode, and control electrodes; a direct conductive connection from the anode of said first tube to the control electrode of the second tube; a source of energy for supplying potentials to said electrodes; means including circuit connections from said anodes to the positive terminal of said source of energy, resistance means in said circuit connections for maintaining the anode potential of said first tube in predetermined relation with 1,sea,aea

cluding circuit connections from said anodes to the positive terminal of saidsource of energy, resistance means in said circuit connections for maintaining the anode potential of said first tube in predetermined relation with respect to the anode potential of the second tube; means including circuit connections from the cathodes of said tubes to the negative terminal of said source of energy; resistance means in said last mentioned circuit connection for maintaining predetermined relations between said cathodes; and a resistance circuit connection from the cathode of said second tube to the positive electrode of said source of energy.

12. In a vacuum tube cascade system comprising a first tube; a second tube; both of said tubes having cathode, anode, and control electrodes; a direct coupling connection from the anode of said first tube to the control electrode of said second tube; a source of anode potential forsaid tubes, said tubes being connected across said source substantially in parallel; and resistance biasing means in series with said tubes for producing proper operating potentials for said second tube.

13. In a vacuum tube cascade system comprising a first tube; a second tube; both of said tubes having cathode, anode, and control electrodes; a direct coupling connection from the anode of said first tube to the control electrode of said second tube; a source of anode potential for said tubes, said tubes being connected across said source substantially in parallel; resistance biasing means in series with said tubes for producing proper operating potentials for said second tube; and at least one further circuit including biasing resistance means extending from the positive pole of said source over the cathode of said second tube to the negative pole of said source.

14. In a vacuum tube cascade system as described in claim 13 in which said first tube includes a screen grid electrode whereby said further circuit extends from the positive pole of each of said tubes to one terminal of said part of said first tube to the cathode of said second tube.

15. In a vacuum tube cascade system as I source through a biasing resistor to the oathode of said second tube.

16, In a vacuum tube cascade system comprising a first tube; a second tube; both of said tubes having anode and control electrodes; a direct coupling connection from said anode of said first tube to the control electrode of said second tube; a source of anode potential for said tubes, the anode of said first tube being connected to the positive p Jle of said source in series with a biasin resistance and the cathode of said first tube being connected to the negative pole of said source, the anode and cathode of said second tube being also connected to the positive and negative pole of said source, respectively; and resistance biasing means in the cathode connection of said second tube for producing proper operating potentials for said second tube.

17. In a vacuum tube cascade system comprising a first tube; a second tube; both of said tubes having anode, cathode, and control electrode; a direct coupling connection from said anode of said first tube to the control electrode of said second tube; a source of anode potential for said tubes, the anode of said first tube being connected to the positive pole of said source in series with a biasing resistance and the cathode of said first tube being connected to the negative pole of said source, the anode and cathode of said second tube being also connected to the positive and negative poles of said source, respectively; resistance biasing means in the cathode connection of said second tube for producing proper operating potentials for said second tube; and at least a further direct current circuit including biasing resistance means extending from the positive pole of said source over the cathode of said second tube to the negative pole of said source.

18. In a vacuum tube cascade system as described in claim 17 in which said first tube includes a screen-grid electrode whereby said further circuit extends from the positive pole of said source through the anode-screen grid path of said first tube over the cathode of said second tube to the negative pole of said source.

19. In a vacuum tube cascade system as described in claim 17 in which afurther circuit extends from the positive pole of said source through a biasing resistor over the cathode of said second tube to the negative pole of said source.

In testimony whereof I afiix my signature.

DR. ERICH ASCII. 

